Growth performance, fillet quality and immunity after challenge with streptococcus agalactiae of red tilapia ( oreochromis sp .) fed diet containing cysteamine and creatine

Abstract

This study aimed to evaluate the effect of creatine and cysteamine supplementation on the growth performance, fillet quality and resistance to bacterial infection of Streptococcus agalactiae in red tilapia. Five types of experimental diet (quadruplicate) with the same energy and protein content were tested. These consist of N (negative control), A (0.5 g/kg cysteamine), B (0.4 g/kg creatine), C (0.5 g/kg cysteamine plus 0.4 g/kg creatine) and D (0.25 g/kg cysteamine plus 0.2 g/kg creatine). Male red tilapia (Oreochromis sp.), with average body weight of 49.51 ± 4.90 g, were kept in 175-L tank at 10 fish/tank density for 56 days rearing period. The challenge test was carried out through injecting fish (body weight: 152.05 ± 12.2 g) with S. agalactiae 107 CFU/ml as much as 0.10 ml/fish. The results showed that treatment C (0.5 g/kg cysteamine plus 0.4 g/kg creatine) increased (p < 0.05) levels of protein retention, activity of superoxide dismutase (SOD) of the liver (p < 0.05), but decreased levels of malondialdehyde (MDA) and liver glycogen (p < 0.05). This last condition was followed by a decrease (p < 0.05) in plasma protein levels that resulted in a decline (p < 0.05) of water content and MDA of fillet after stored for 24 h. In addition, treatment C increased fish resistance to S. agalactiae infection, demonstrated by higher survival rate and lysozyme activity (p < 0.05). In conclusion, the treatment C boosts protein retention, fillet quality and robustness to pathogenic bacterial infections.